Sleep apnea syndrome is due to episodic upper airway obstruction during sleep. As a consequence, there is severe interruption of sleep in the patient. Positive airway pressure devices, such as CPAP, and bi-level positive airway pressure devices have been developed to treat this disorder. CPAP devices deliver positive air pressure to the nasal passages of patients during sleep in order to maintain their airways in a continuously open state. In BiPAP therapy, pressure is applied alternately at relatively higher and lower prescription pressure levels.
A typical PAP device comprises a flow generator (e.g., a blower) which receives air from any suitable source such as a pressurized bottle or the ambient atmosphere. The gas flow from the flow generator is passed via a delivery conduit to a patient interface, such as a mask.
Humidifiers have been developed for use with PAP devices to humidify the air supplied to the patient. A typical humidifier comprises a water reservoir connected in series with the delivery conduit between the flow generator and the patient interface. A problem associated with these humidifiers is the possibility of water from the humidifier entering the PAP device through the delivery conduit and potentially causing damage to the device.
Many PAP devices are also used in combination with a therapeutic gas such as oxygen which is generally delivered at the patient end of the delivery conduit. A problem associated with the use of therapeutic gas is when positive pressure from the flow generator is lost, the therapeutic gas will flow through the delivery conduit to the PAP device potentially causing damage to the device.
The pressure sensitive flow control valve of the present invention has been developed to overcome the problem of water from a humidifier and other contaminants from entering the PAP device by blocking the outlet of the PAP device to restrict the path of entry for the contaminants. Also, the valve prevents the flow of gas, in the absence of positive pressure, back into the PAP device or ventilator by providing a low resistance exit path to atmosphere for any gas or water in the patient circuit.